The daughter of Authorized, a Listed winner last year, was a little fresh in the early stages and raced keenly under Ryan Moore.
Moore switched her to the far rail to make his challenge and Ambivalent picked up well. The eventual winner, Dalkala had areadly had a race this season and got first run.
Ambivalent was gaining with every stride but the line came too soon and she was beaten by a length.
Roger said: "That was a very pleasing effort on her first start of the year. She was a little fresh early on but has come home well.
"This was a bit shy of her best trip and we'll probably go a mile and a half now, with a race like the Pinnacle Stakes at Haydock a possible option for her."
Ambivalent under William Nadal on Warren Hill